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Re^4: Error handling - how much/where/how?

by Jenda (Abbot)
on Jun 16, 2005 at 00:43 UTC ( #467123=note: print w/ replies, xml ) Need Help??


in reply to Re^3: Error handling - how much/where/how?
in thread Error handling - how much/where/how?

No, I'm not gonna hate any or traits. You are missing the point. I just won't put up with a module that forces me to jump throught the hoops to get at the value. That was the main point, not the fact that the hash did not contain the error details.

If the operation failed there's no point in it returning "something consumable by the main-line client code". The main-line code should NOT consume the value at all! Which, using your style means that I have to test everywhere and then on a hundred more places whether the thing I received is indeed a value or an error. Which means that 1) the code will be much longer and 2) I will surely forget to test it on some places.

Why is your division operator returning 1? How is 1 "usable but identifiably bogus"? 1 is a totaly reasonable result of division, even if it's bogus in some cases (using your division operator) there's nothing identifiable about it.

And for your division operator to be at least barely useable you'd have to define it not (just) on numbers, but also on your "maybevalues". That is on those {value =>..., 'is-valid'=>...,...} structures? And you'd likewise need to define all the other mathematical operators. So that the user may at least (mind you I'm not asking for anything fancy) write code like $mayberesult = 1+ $x/$y (assuming the / is that your division operator. Of course that code would not be complete, after that the user would have to add something like

if ($maybevalue->{'is-valid'}) { ... } else { report the problem somehow, maybe return another maybevalue from the +current procedure }
You like this code? Well I don't.And I don't believe noone ever looks at the $maybevalue->{value} without consulting $maybevalue->{'is-valid'} first.

Next thing. What's the result of {value => 1, 'is-valid'=>0,error=>'Division by zero'} / {value => 1, 'is-valid'=>0,error=>'Number outside representation range'}? Do you choose just one of the errors? Do you combine them? How? And if you keep the trace, how do you combine that? And how's the "main-line code" supposed to make any use of that then?

Exceptions let me handle the problems at the level I need, without caring at the deeper levels. Which may mean that I won't know where exactly in some computation does the div-by-zero originate from ... but most likely I don't care. I just need to handle the problem without blowing he code out of proportions with tons of maybevalue handlings. We have a job to do and it's not to write a program you can prove to be correct, but rather to write a program that does what it's supposed to and to do so in a reasonable time.

Jenda
XML sucks. Badly. SOAP on the other hand is the most powerfull vacuum pump ever invented.


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